Automated vehicle control along highways or other types of roadways has long been desirable as a way of addressing the ever-increasing vehicle traffic. By automatically controlling the movement of vehicles along a highway or other roadway without the need for human intervention, the hope is that traffic congestion and delays will be minimized, and that the resulting traffic flow will be much smoother. One aspect of such an automated vehicle control system involves relatively accurately assessing the position of the vehicle relative to the pathway and, where necessary, appropriately steering the vehicle to ensure that the vehicle is appropriately guided along the pathway.
Systems have been proposed in the past for automatically controlling the vehicle steering operation in a manner that causes the vehicle to move along a predetermined path. One such system, which is disclosed in U.S. Pat. No. 5,347,456, utilizes magnetic markers that are embedded along the desired road or pathway. The vehicle is outfitted with a magnetic sensor that detects the magnetic markers as the vehicle moves along the roadway. Signals produced by the magnetic sensor through detection of the magnetic markers are processed by a computer. The computer then controls the steering operation of the vehicle so that the vehicle moves along the desired path.
Another system, which is disclosed in U.S. Pat. No. 4,333,147, utilizes inductive markers that are embedded along the roadway. In this system, the vehicle is provided with a detecting coil that detects the inductive markers. Signals produced by the detecting coil are utilized for guiding the vehicle along the desired path.
The system disclosed in U.S. Pat. No. 4,049,961 employs passive responders or optical reflectors that are embedded along the boundaries of the roadway defining the desired path of movement for the vehicle. Laser transmitter/receiver units are provided on the vehicle to emit a light signal that covers a certain number of the responders. The responders reflect a fraction of the emitted light and the received reflected signals are used to form an electrical signal whose amplitude and sign are indicative of the position of the transmitter along an axis transverse to a reference axis. The vehicle is then guided on the basis of these signals.
Systems such as those described in the aforementioned patents suffer from the disadvantage that in order to implement such systems, significant modification of existing roadways must be performed. That is, the roadways must be outfitted with or have embedded therein magnetic markers, inductive markers or optical reflectors. As can be readily appreciated, the need to outfit existing roadways with these additional infrastructures renders these systems quite expensive and possibly cost prohibitive. Further, considerable time and effort would be required to modify existing roadways in a manner that will permit implementation of these systems. Thus, from a practical standpoint, these systems do not represent truly effective alternatives for use in successfully implementing the automated guidance of vehicles.
Another known vehicle guidance system is disclosed in U.S. Pat. No. 4,630,109. In this system, the vehicle is outfitted with a CCD camera that periodically scans the roadway to detect an optically distinct line extending along the roadway. Signals representing successive scans of the CCD camera are stored and then correlated to determine lateral movement of the vehicle between successive scans. This information is then used to guide the vehicle along the roadway.
While this system does not necessarily require extensively outfitting existing roadways with additional infrastructures to the same extent as the other systems described above, this system does suffer from the disadvantage that proper detection of the optically distinct line requires a very complicated image processing system. Further, images captured by the CCD camera can vary widely depending upon a variety of factors such as sunlight, weather and the like so that the accuracy of the system may be somewhat suspect.
At least some of the previously proposed vehicle guidance systems suffer from other drawbacks as well. For example, some systems are not well suited to accurately and rather simply detecting the yaw angle of the vehicle. This can have an impact on the operation of the system since the orientation or yaw angle of the vehicle affects the amount by which the vehicle steering must be altered to direct the vehicle along the intended path of movement.
In addition, at least some of the previously proposed systems are not well suited for use in connection with aspects of automated vehicle guidance other than maintaining the position of the vehicle in a particular lane. That is, automated vehicle guidance involves not only guiding the movement of the vehicle in a lane, but other aspects of vehicle travel such as lane changing and the detection of vehicles or other objects in adjacent lanes so that lane changing does not occur at an inappropriate time.
In view of the foregoing, a need exists for an automated system and method for guiding moving objects such as vehicles along a predetermined desired path that is not susceptible to the same disadvantages and drawbacks associated with other known systems. Further, a need exists for a system and method for automated guidance of moving objects such as vehicles that does not require complicated image processing capabilities and also does not require the addition of costly infrastructures to existing roadways.